Domains How many free

When i signed up for plusnet 2 years ago i opted for the .co.uk domain at 1 pound a month.Looking at my account it says i can have up to 5 hosted.Does this mean i can have my xxxxxxx.co.uk site & register another 4 xxxx.co.uk sites but still only pay the pound a month for all 5?Im on the plusnet premier account btw.Thanks in advance.Pete.